Recently, research and business communities show a great interest in the Local Positioning System (LPS) technology. Unlike the Global Positioning System (GPS, Galileo, GLONASS, QZSS), LPS systems allow indoors localization. In order to locate an object within a certain area, a wireless infrastructure needs to be installed. As a rule, indoors, the localization accuracy depends on the spatial density of anchor nodes. Those anchors are used to measure distances to mobile nodes.
Real-time positioning systems are based on wireless networks which can utilize different methods of distance of measurement: Time-of-Flight (ToF), Angle-of-Arrival (AoA) and Received Singal Strength (RSS). Methods based on Time-of-Arrival (ToA), Time-Difference-of-Arrival (DoA), Round-Trip-Time (RTT) are referred to the ToF methods group. First two methods (ToA and TDoA) do require sy;stem time synchronization between all nodes in the system, whereas the RTT method does not. Obviously, distance measurements based on the RSS are relatively inaccurate, especially in a case of substantial distance between nodes. However, knowing of the RSS value is very important for applications with room-level accuracy indoors: room walls create a drop in a signal strength, which is used to reliably determine the room where the mobile object in is. This technique is widely used in RSS patterns methods [1,2].
Along with the localization capability, wireless networks provide data communications channels between nodes. Commercial LPSs use various radio technologies: Wi-Fi, ZigBee, UWB, nanoLOC, NFC RFID, etc. This paper presents an overview of the RealTracTM technology developed by the RL-Service ltd. It is based on the nanoLOC (IEEE 802.15.4a) radio standard. The RealTracTM technology combines good data transfer rate with low power consumption of radio devices, location estimation and voice communication feature at the same time.
The rest of this paper is organized as follow. Section 2 describes architecture of the RealTracTM technology; technical characteristics of devices used; data transfer protocols for communication between radio modules in the system and between a client and a server. Section 3 is devoted to the applied location estimation algorithms based primarily on the particle filter. ToF and RSS values, building structure, constraints on object velocity and data acquired from the embedded inertial measurement unit (IMU) are taken into a consideration. The opportunity of using the precise air pressure sensor is utilized for the floor identification and for the estimation of the relative height. Those features are based on the atmospheric pressure data of all devices in the system. Section 4 concludes the development work and briefly describes possible applications of the described technology and defines future development directions.
RealTrac Access Point
RealTrac Access Point is stationary equipment, included in the Real Time Location System RealTrac. This device is the element of the Real Time Location System RealTrac, providing its work, and has to be built in the wall, ceiling, shaft, post or other element of the construction.
RealTrac Tag – compact location device. Depending on necessity, the body can be of different size, from tiny, as the coin, till larger one, but placing in the palm! RealTrac Tag can be carried in the hand
RealTrac Sentry is a mobile digital radio station with the function of detection of person’s location indoors and outdoors.
RealTrac Rio Intercom
RealTrac Rio Intercom is a graceful location and communication device for the personal use. The body of Rio Intercom is ergonomic, comfortable for handling. The device can be carried on laces, on belt, in pocket or in wallet.
RealTrac Bradz is a special device for personal use, designed for the secret services and state bodies of the system of execution of punishment.
RealTrac Analyzer is a professional autonomous device, used upon installation and maintenance of the local positioning system RealTrac